Who: Mohammadreza Farooghi-Mehr
When: December 4th, 2024, 10:30 AM
ZOOM: https://unl.zoom.us/j/98216680381
Title: Dynamics of Flexible Freestanding Structures Under Ground Motion Excitation
Abstract: Freestanding structures are characterized by being unattached at the base, exhibiting rigid or flexible motion under ground motion excitation with various potential responses including rocking (rotation at the base about corner points), pure sliding, slide-rocking, and overturning. While rigid freestanding structures have been extensively studied, the behavior of flexible freestanding structures—particularly the interaction between modes involving sliding—remains underexplored. This dissertation develops novel analytical models that integrate three degrees of freedom—deformation, rocking, and sliding—along with updated criteria for mode initiation, transition, and impact mechanisms (the primary source of energy dissipation in freestanding structures). An experimental program was conducted using a steel tower with stiffeners, attached mass weights, and a concrete pad. The results reveal that sliding is a critical factor contributing to the overturning failure of squat flexible structures, contrary to the expectation of minimal overturning for these configurations. Additionally, a correlation between significant sliding displacements and twisting in tall structures suggests the occurrence of complex three-dimensional motion patterns.